JP5204558B2 - Discharge measuring device for impulse test and discharge discrimination method - Google Patents

Description

  The present invention relates to a discharge measuring device that determines the presence or absence of a discharge that progresses along an insulating medium or an insulator inside an electric power device during an impulse test, and a discharge determination method thereof.

In a conventional insulation failure inspection apparatus for rotating electrical machines, partial discharge generated when an impulse voltage application test is performed is detected by the following method to determine failure.
That is, first, a discharge electromagnetic wave generated when a product to be inspected is partially discharged due to poor insulation is detected by an electromagnetic wave sensor, and simultaneously, a discharge current flowing from the product to be inspected through a ground line is detected by a current sensor. Next, spectrum analysis is performed on the measured discharge electromagnetic wave signal and the discharge current signal by Fourier transform.
At the same time, a band in which the spectrum when it occurs is characteristically increased compared to when no partial discharge occurs is measured for the discharge electromagnetic wave signal and the discharge current signal, and these are respectively measured as FB1 and FB2. And
Finally, the electromagnetic wave spectrum intensity and the current spectrum intensity are obtained by integrating the discharge electromagnetic wave signal and the discharge current signal in FB1 and FB2, respectively. If both of these are equal to or greater than a predetermined standard value, partial discharge occurs. It is determined that there is a failure (see, for example, Patent Document 1).

JP-A-2005-274440 (page 6-8, FIG. 1-6)

When the conventional method is applied to oil-insulated equipment having a test voltage of several tens of kV level, an impulse tester using a semiconductor element does not generate any air discharge signal directly radiated from the impulse tester to the measuring instrument. Even in the impulse tester using the air gap, the level of the air discharge signal was not so high. In addition, since the air discharge signal has a signal intensity distribution with a peak at a frequency different from that of the oil progressing discharge signal, which is a problem in the insulation performance of the electrical equipment, the oil progressing discharge signal is determined from the air discharge signal in the frequency domain. It was possible to distinguish.
However, for oil-insulated power equipment used at high voltages such as power transformers, it is necessary to test by applying an impulse voltage with a peak value of several hundred kV to several thousand kV, which is emitted from the impulse testing machine. The level of the air discharge signal is extremely high.
In this case, the intensity in the vicinity of the base out of the peak of the spectrum of the air discharge signal also increases, and the peak value of the spectrum of the in-oil progressing discharge signal existing in this region is buried in the base, so that the frequency domain However, there is a problem that the progressing discharge signal in oil cannot be distinguished from the air discharge signal.

  The present invention has been made to solve the above-described problems, and obtains a discharge measuring device that can reliably determine the occurrence of a progressing discharge in oil generated in an oil-insulated power device. For the purpose.

In the discharge test apparatus for impulse test according to the present invention, a progress detection in oil is generated by a pulse detected by the discharge detection sensor and the discharge detection sensor within a predetermined period after the impulse test voltage is applied to the power device. In the pulse test discharge measuring apparatus, the signal determination unit masks the pulse train signal and excludes the pulse train signal for a predetermined period after applying the impulse test voltage. For the three conditions that the level is a predetermined value or more, the duration of the pulse train is a predetermined value or more, and the generation frequency of the pulse train is a predetermined value or more, the number of occurrences of pulses that satisfy the three conditions and have a signal level of the predetermined value or more. The total value is greater than or equal to a predetermined value, or the total duration of pulse trains satisfying the three conditions and having a signal level greater than or equal to the predetermined value is greater than or equal to the predetermined value In some cases, it is determined that the oil progress discharge occurred.

  According to this invention, by providing the determination unit in the discharge measuring device for impulse tests, it is possible to reliably determine the progressing discharge in oil generated in the electric power equipment from the air discharge radiated from the impulse testing machine. There is an effect that can be.

Embodiment 1 FIG.
FIG. 1 shows an impulse discharge measuring device for oil-filled power equipment in the present embodiment. An electromagnetic wave sensor 2 for detecting discharge electromagnetic waves is installed on the tank flange surface of the electric power device 1 whose inside is filled with insulating oil. A signal detected by the electromagnetic wave sensor 2 is input to the log amplifier 4 through the high pass filter 3. The reason why the log amplifier 4 is used is to prepare the log amplifier 4 having a specification that can cope with the dynamic range of the pulse peak value of the discharge signal to prevent the detection of the discharge signal from being detected.
The output signal logarithmically converted by the log amplifier 4 is input to the signal determination unit 5. The signal determination unit 5 also receives a signal from a voltage measurement unit 7 configured by a voltage divider or the like that measures the output voltage of the impulse power supply 6. In the signal determination unit 5, based on the characteristics of the waveform of the discharge electromagnetic wave signal that is the output signal from the log amplifier 4 and the impulse signal that is the output signal from the voltage measurement unit 7, the presence or absence of the discharge signal generated inside the power device, The display device 8 displays the determination result.

The discharge modes observed in the insulating oil during the impulse test are roughly divided into two types as schematically shown in FIG. As shown in FIG. 2 (a), the discharge is locally generated only in the electric field concentration portion (local discharge), and the other is the discharge generated in the electric field concentration portion as shown in FIG. 2 (b). It is a discharge mode (progressive discharge) that has progressed in oil or along the surface of the insulating barrier 10 like lightning. The discharge inside the device that is at risk of dielectric breakdown during the impulse test is a progressive discharge as shown in FIG. 2B, and the local discharge is not a problem in a single test such as the impulse test.
The electromagnetic wave sensor 2 of the discharge measuring device receives the above-mentioned progress signal in oil, the local discharge signal in oil, and the air discharge signal generated in the air gap 9 of the impulse power supply 6. In order to achieve the purpose of the present discharge measuring device, ie, the insulation performance verification of No. 1, it is sufficient that the signal determination unit 5 can determine the in-oil progress discharge signal from other signals.

Next, a method for discriminating the in-oil progress discharge signal generated in the power equipment from the local discharge signal in the oil, the air discharge signal, and other external noise based on the result of the element model test in the insulating oil. To do.
An element model of a rod-plate electrode system is set in insulating oil, an impulse voltage output from the high voltage power source 6 is applied between both electrodes, and a voltage measuring unit is used using the discharge measuring device shown in FIG. 7 and a measurement example in which the output of the log amplifier 4 is measured are shown in FIG. In addition, although not shown in FIG. 3, in this test, the state of discharge emission by photography and the time measurement of the discharge emission signal by the optical sensor are simultaneously performed. The presence / absence, and the progress discharge and the local discharge can be discriminated.

3A shows an impulse voltage waveform that is an output from the voltage measuring unit 7, and FIGS. 3B to 3E show outputs from the log amplifier 4, respectively. The horizontal axis (time axis) is plotted with (a) to (e) so that the timing with the voltage waveform can be understood.
FIGS. 3B and 3C are examples when no discharge is observed in the photograph or the optical sensor. In FIG. 3B, the output from the log amplifier 4 includes noise immediately after the impulse voltage is applied. In FIG. 3C, the air discharge signal is detected in a single period during the impulse falling period in addition to the noise immediately after the impulse voltage is applied.
3 (d) and 3 (e) are examples when a discharge in oil is observed with a photograph or an optical sensor. In FIG. 3 (d), not only immediately after the application of the impulse voltage but also in the period of the impulse falling. Only the air discharge signal and the oil discharge signal that occur once are detected, but FIG. 3 (e) includes a signal that is frequently detected in a continuous period. However, it differs from FIG.

  Therefore, the signal patterns when the in-oil discharge shown in FIGS. 3D and 3E are generated can be classified into the following two types. The first pattern is a pattern in which signal pulses are detected once as shown in FIG. In the second pattern, as shown in FIG. 3E, signal pulses are frequently detected over a period of approximately 5 μs or more, and such a period in which signal pulses are frequently detected intermittently occurs. . The mode of discharge when a single pulse signal such as the first pattern was detected was local discharge as a result of photography or observation by an optical sensor, and there was no progress discharge. On the other hand, when a high-frequency pulse signal that continues for a certain time or more as in the second pattern is intermittently detected, the discharge mode may be both local discharge and progressive discharge.

On the other hand, the signal patterns shown in FIGS. 3B and 3C when no discharge in oil occurs can be classified into the following two types. The first pattern is a pattern that is detected in common in FIGS. 3B to 3E, and a signal is generated for 5 to 10 μs immediately after the impulse voltage rises. This signal is an air discharge signal in the air gap 9 that is generated when an impulse voltage is generated, and is always generated during an impulse test of several hundred kV or more due to the voltage generation principle of the impulse power supply 6. As shown in FIG. 3C, the second pattern is a pattern in which a signal pulse is detected once at the falling edge of the impulse.
The findings obtained from the experimental results shown in FIG. 3 can be summarized as shown in Table 1.

From the above, the pulse that occurs once may be excluded as a result of air discharge or local discharge in oil, and in order to capture the progressing discharge in oil shown in FIG. It is only necessary to target only a pulse train including a frequent pulse that continues as described above. As a result of further detailed analysis of the discharge waveform including such a pulse train, it was found that the following conditions were required.
(1) The signal level (Lp) of the pulse included in this pulse train is equal to or higher than the noise level (L1).
(2) A group of pulse trains has a duration (Tp) greater than or equal to a predetermined value (T1). From the above experimental results, it was found that the predetermined value T1 can be determined by setting it to 5 μs.
(3) The generation frequency (Fp) of pulses within a group of pulse trains is not less than a predetermined value (F1). From the above experimental results, it was found that the predetermined value F1 can be determined by setting it to 400 kHz.
Note that even pulse trains having the above three characteristics include those of local discharge, so that it is necessary to narrow down the conditions as described below.

For a plurality of pulse trains having the above three conditions generated within a predetermined period after application of an impulse, the total number of times that the pulses included in these pulse trains are generated (sum (Cp)) is shown on these horizontal axes. The sum of the durations (sum (Tp)) is plotted on the vertical axis and plotted for each discharge result. Based on the result of photography or measurement by an optical sensor, progress discharge in oil and air discharge or local in oil The result of discriminating from discharge is shown in FIG. Here, the predetermined period after applying the impulse refers to a period until the impulse is attenuated, but in this embodiment, JEC (Institute of Electrical Engineers of Japan, Electric Planning Research Committee) 0301 “Static inductor impulse withstand voltage test” Therefore, the time is 400 μs, which can be said to be the time when the voltage becomes almost zero.
From this result, the distribution is clearly different between the progressing discharge in oil, the local discharge in oil and the air discharge. Therefore, in addition to the above conditions (1) to (3), those satisfying at least one of the following conditions (4) or (5) can be reliably discriminated as progressing discharge in oil.
(4) The total number of pulse generations (sum (Cp)) within a predetermined period after applying the impulse is equal to or greater than a predetermined value (C2). In the analysis result in FIG. 4, the predetermined value C2 is 20 times.
(5) The total duration (sum (Tp)) of the pulse train is equal to or greater than a predetermined value (T2) within a predetermined period after applying the impulse. In the analysis result in FIG. 4, the predetermined value T2 is 20 μs.

The above discharge determination method can be explained by the following concept. The progressing discharge in oil is considered to occur probabilistically in a situation where the applied voltage exceeds a certain threshold value. When the impulse application voltage is increased, the time during which the voltage is applied exceeding the threshold value during the impulse decay period (400 μs in the present embodiment) becomes longer. Accordingly, the number of pulse generations during the impulse decay period increases, and the total duration of the pulse train also increases. That is, the withstand voltage performance of the device is closely related to the number of pulse generations in the impulse test and the duration of the pulse train.
If the basic idea as described above is used, threshold values of L1, T1, F1, C2, and T2 are experimentally obtained for power devices using various insulating oils and power devices having different shapes. This makes it possible to determine the progressing discharge in oil.

The discharge waveform can be determined according to the determination flow shown in FIG. 5 on the basis of the determination criteria for the progressing discharge in oil obtained from the element test results described so far.
In step 1, first, it is confirmed whether or not the pulses in one pulse train satisfy the necessary conditions described in (1) to (3) described above. When the impulse voltage rises, the level of the discharge signal generated by the flashing of the air gap 9 of the impulse power supply 6 is extremely large, and it is difficult to reduce the level of this signal no matter how frequency filtering is performed. Discharge signal cannot be measured. Accordingly, during a predetermined period (typically 5 to 10 μs) immediately after the rise of the impulse, the signal from the log amplifier 4 is masked and excluded from the waveform monitoring target. If a pulse train satisfying all of the above (1) to (3) is detected in a period other than the mask period, the process proceeds to step 2; otherwise, it is determined that there is no progressing discharge in oil.
In step 2, since the pulse train selected in step 1 may include both the in-oil progress discharge signal and the in-oil local discharge signal, the pulse train is further narrowed down according to the above condition (4) or (5). Extract only medium progress discharges. As can be seen from the graph of FIG. 4, the determination may be made by either one of the conditions (4) and (5), or both conditions may be used.

The basic criteria for determining the discharge waveform and the flow thereof have been described above. In the following, various measures for further improving the accuracy of discrimination, such as reducing external noise and improving sensor sensitivity, will be described.
FIG. 6 is a view for explaining an attachment location and an attachment method of the electromagnetic wave sensor 2. As shown in FIG. 6A, the electromagnetic wave sensor 2 is generally attached to an outer surface portion of a lid plate 12 made of an insulating material such as acrylic provided on a flange portion of a tank 11 of a power device. Here, in FIG. 6A, since the electromagnetic wave sensor 2 is not shielded from the outside, the electromagnetic wave sensor 2 is shielded by a metal case 13 or the like as shown in FIG. 6B to improve noise resistance. Is preferred. In this case, in order to obtain a sufficient shielding effect, the metal case 13 is preferably electrically connected to the tank 11 of the power device. Further, as shown in FIG. 6C, the electromagnetic wave sensor 2 may be installed in the tank by providing, for example, an insulating plate 14 so as to keep insulation from the tank, and a metal lid plate 15 may be attached. In the case of the structure as shown in FIG. 6C, the electromagnetic wave sensor 2 is installed inside the electric power device 1, so that the electromagnetic wave sensor 2 is disposed close to the high voltage portion to cause discharge. Care must be taken so that nothing happens.

  The high-pass filter 3 inserted between the output of the electromagnetic wave sensor 2 and the input of the log amplifier 4 is external noise picked up by a measurement line connecting the electromagnetic wave sensor 2 and the log amplifier 4, and in particular, the band of the electromagnetic wave sensor 2. It is provided to exclude low frequency ones. The cut-off frequency of the high-pass filter 3 is desirably equal to or higher than the cut-off frequency on the low frequency side of the electromagnetic wave sensor 2. Further, since the electromagnetic wave sensor 2 has a certain degree of detection sensitivity even in a range other than the specification detection band, noise in this band can also be excluded by the high-pass filter 3. In order to obtain a sufficient filter effect, the high pass filter 3 is preferably connected immediately before the input terminal of the log amplifier 4.

  FIG. 7 shows a frequency spectrum obtained by Fourier transforming an air discharge signal and an oil discharge signal. The oil discharge signal contains a signal component having a higher intensity in the high frequency band than the air discharge signal. I understand. Therefore, by using the electromagnetic wave sensor 2 having particularly sensitivity in such a high frequency band, the sensitivity to the oil discharge signal is increased as compared with the air discharge signal as compared with the case of using the broadband sensor. It is possible to improve the accuracy of the oil discharge signal discrimination. Since the discharge signal in oil has a higher intensity in the band of about 200 MHz or more, particularly 700 MHz or more than the air discharge signal, the detection band of the electromagnetic wave sensor 2 is also selected to be about 200 MHz or more, more preferably 700 MHz or more. It is good to do.

  In the above-described method, the detection band of the electromagnetic wave sensor 2 itself is limited by selecting a band suitable for the strong band of the discharge signal in oil. However, as the electromagnetic wave sensor 2, a broadband sensor is used. The frequency band can also be limited by the high-pass filter 3 inserted between the electromagnetic wave sensor 2 and the log amplifier 4. In this case, the cut-off frequency of the high-pass filter 3 is also preferably about 200 MHz or higher, more preferably 700 MHz or higher.

  As described above, according to the discharge measuring apparatus of the present embodiment, since the signal determination unit 5 that performs the determination of the discharge waveform according to the determination criterion and the flow described above is provided, it is difficult to take a photograph or observe with an optical sensor. Even in the case, the in-oil progress discharge signal generated inside the electric power device 1 can be reliably determined from the air discharge signal radiated from the impulse power supply 6 and the oil local discharge signal.

Embodiment 2. FIG.
FIG. 8 is a diagram showing an impulse discharge measuring apparatus for electric power equipment according to Embodiment 2 of the present invention. In the first embodiment, the electromagnetic wave sensor 2 is used as the discharge detection sensor. However, the present embodiment is different in that the current sensor 21 is used. The current sensor 21 is installed on the ground line of the power device 1 and detects a high-frequency discharge current when a discharge occurs. Since the configuration and operation of other devices are the same as those in Embodiment 1, description thereof is omitted.
When the current sensor 21 is used, although the rising speed of each pulse is a little slower than that of the electromagnetic wave sensor, the pulse repetition frequency and the pulse duration are almost the same. (1) to (5) can be applied as they are. Therefore, it can be determined according to the discharge waveform determination flow shown in FIG.

Similarly to the electromagnetic wave sensor 2, the current sensor 21 is preferably a sensor having detection sensitivity in a frequency band in which the oil discharge signal is higher in intensity than the air discharge signal. It is difficult to make a narrow-band sensor such as the electromagnetic wave sensor 2. Therefore, in this embodiment, it is desirable to connect the high-pass filter 3 that limits the frequency band between the current sensor 21 and the log amplifier 4 to remove signals in the low frequency region. The cut-off frequency is the same as in the first embodiment.

As described above, according to the discharge measuring device of the present embodiment, since the signal determination unit 5 that performs the determination of the discharge waveform by the flow and the determination criteria similar to those described in the first embodiment is provided, Even when observation with an optical sensor is difficult, it is possible to reliably discriminate the in-oil progressing discharge signal generated in the power device from the air discharge signal radiated from the impulse power supply 6 and the oil local discharge signal. .
Furthermore, in the present embodiment, unlike measuring electromagnetic waves propagating in space as in the first embodiment, the current sensor 21 is used to measure only a localized ground wire, so that an electromagnetic shield, etc. Even if this measure is not taken, there is an advantage that it is relatively insensitive to external noise. Furthermore, since it is possible to measure by simply clamping the ground wire of the power device 1, there is an advantage that it is not necessary to incorporate in the power device 1 in advance and the measurement can be easily performed.

It is a figure which shows the structure of the impulse discharge measuring device of Embodiment 1 of this invention. It is a figure explaining two aspects of the discharge in oil at the time of an impulse test. It is a figure which shows the example of a measurement of the applied voltage waveform at the time of an impulse test, and a log amplifier output waveform. It is the figure which plotted about the sum total of the frequency | count of pulse generation, and the sum total of the duration of a pulse train, in order to discriminate | determine progress discharge in oil. It is a figure which shows the determination flow of a discharge waveform. It is a figure which shows the installation method of the electromagnetic wave sensor used in Embodiment 1 of this invention. It is a figure which shows the frequency spectrum which carried out the Fourier transformation of the air discharge signal at the time of an impulse test, and the oil discharge signal. It is the figure which showed the structure of the impulse discharge measuring device of Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power apparatus 2 Electromagnetic wave sensor 3 High pass filter 5 Signal determination part 21 Current sensor

Claims (6)

A discharge detection sensor, and a signal determination unit that determines that a progressing discharge in oil has occurred due to a pulse detected by the discharge detection sensor within a predetermined period after the impulse test voltage is applied to the power device. In the pulse test discharge measuring apparatus, the signal determination unit masks the pulse train signal for a predetermined period after applying the impulse test voltage to exclude the pulse train from being monitored, the pulse train signal level is equal to or higher than a predetermined value, and the duration of the pulse train is With respect to the three conditions of a predetermined value or more and the occurrence frequency of the pulse train being a predetermined value or more, the total value of the number of pulse occurrences satisfying the three conditions and having a signal level of the predetermined value or more is a predetermined value or more, or It is determined that a progressing discharge in oil has occurred when the total duration of pulse trains satisfying the three conditions and having a signal level equal to or higher than a predetermined value is equal to or higher than a predetermined value. Impulse test discharge measurement device.   The impulse measurement discharge measurement apparatus according to claim 1, wherein the discharge detection sensor has detection sensitivity in a frequency region in which a level of the oil discharge signal is higher than the air discharge signal in the frequency spectrum of the signal.   3. The filter according to claim 1, further comprising a filter having a pass band in a frequency region in which a level of the oil discharge signal is larger than the air discharge signal in the frequency spectrum of the signal on the output side of the discharge detection sensor. Discharge measuring device for impulse tests.   The impulse measurement discharge measurement apparatus according to any one of claims 1 to 3, wherein the discharge detection sensor is an electromagnetic wave sensor.   The impulse measurement discharge measuring apparatus according to any one of claims 1 to 3, wherein the discharge detection sensor is a current sensor. A pulse train detected by the discharge detection sensor is detected within a predetermined period after the impulse test voltage is applied to the power device, and the pulse train signal is masked and excluded from the monitoring target during the predetermined period after the impulse test voltage is applied. A pulse that satisfies the above three conditions and has a signal level that is equal to or higher than a predetermined value for the three conditions that the signal level of the pulse train is equal to or higher than a predetermined value, the duration of the pulse train is equal to or higher than a predetermined value, Progressive discharge in oil when the total number of occurrences is greater than or equal to a predetermined value, or when the total duration of pulse trains satisfying the three conditions and having a signal level greater than or equal to a predetermined value is greater than or equal to a predetermined value Discharging determination method for determining that the occurrence has occurred.

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